The present invention relates generally to the field of electrosurgery, and more particularly to surgical devices and methods which employ high frequency electrical energy to treat tissue in regions of the head and neck, such as the brain and spinal cord.
Cerebrovascular diseases are those in which brain diseases occur secondary to the pathological disorder of blood vessels (usually arteries) or the blood supply. This pathological disorder has a variety of mechanisms, including vessel occlusion by thrombus or embolus, rupture or disease of the blood vessel wall and disturbances in the normal properties of blood flowing through the brain. Regardless of the mechanism, the resultant effect on the brain is either ischaemia/infarction or haemorrhagic disruption (i.e., stroke).
Medical treatment for cerebrovascular disease has included anticoagulant therapy and the use of thrombolytic agents. The effectiveness of anticoagulant agents is uncertain and the risk of recurrent embolic infarction is high. Similarly, thrombolytic agents pose a relatively high risk of intracranial hemorrhage.
Surgical treatment for vascular diseases has included a number of catheter-based approaches, such as balloon angioplasty and endartectomy. Endartectomy procedures typically involve introducing a catheter having a cup-shaped rotating cutter into the vascular system to sever and capture at least a portion of the occlusive material. Other interventional techniques includes laser ablation, mechanical abrasion, chemical dissolution, hot-tipped catheters, drill-tipped catheters and the like. While promising, these techniques have a few drawbacks. For some of these techniques (e.g., balloon angioplasty), it is often difficult to advance the distal end of the catheter through the stenosed region in extremely narrow vessels, such as those encountered in the brain. Under these circumstances, it may be necessary to at least partially recanalize the occlusion before the catheter procedure can begin. Other techniques (e.g., hot-tipped or drill-tipped catheters) rely on very aggressive treatment of the occlusive material to open up a passage. Such aggressive techniques can expose the blood vessel wall to significant injury, for example, vessel perforation.
The present invention is also concerned with the removal of benign or malignant tumors in the head and neck, such as neuromas, meninges, neuroepithelial tumors, lymphomas, metastatic tumors and the like. Unfortunately, conventional techniques for removing such tumors, such as electrosurgery, powered instruments and lasers, are not very precise, and they often cause damage or necrosis to surrounding or underlying body structures, which can be extremely problematic in the brain. Moreover, it is often difficult to differentiate between the target tumor tissue, and other neighboring body structures, such as cartilage, bone or nerves. In particular, many tumors in the head and neck are located closely adjacent to nerves. Nerve injury can lead to muscle paralysis, pain, exaggerated reflexes, loss of bladder control, impaired cough reflexes, spasticity and other conditions. Thus, the surgeon utilizing conventional devices must be extremely careful to avoid damaging the nerves that extend through the target site.
Further, conventional techniques for removing such tumors generally result in the production of smoke in the surgical setting, termed an electrosurgical or laser plume, which can spread intact, viable bacterial or viral particles from the tumor or lesion to the surgical team or to other portions of the patient's body. Numerous studies have confirmed that viable cells, such as papillomavirus, HIV, cancer cells, and the like, are spread to other portions of the patient's body during these tumor removal procedures. In conventional RF devices, for example, a high frequency voltage is applied between two electrodes in either a monopolar or bipolar mode to create intense heat at the target site that causes the inner cellular fluid to explode, producing a cutting effect along the path of the device. This cutting effect generally results in the production of smoke, or an electrosurgical plume, which can spread bacterial or viral particles from the tissue to the surgical team or to other portions of the patient's body. In addition, the tissue is parted along the pathway of evaporated cellular fluid, inducing undesirable collateral tissue damage in regions surrounding the target tissue site.